Catalytic cracking system with pipe formed nozzle body

ABSTRACT

A catalytic cracking system having a spray nozzle assembly adapted for more economical manufacture and efficient performance. The spray nozzle assembly includes an elongated pipe formed nozzle body formed of one or more lengths of cylindrical pipes which define a mixing zone and an elongated barrel extension zone that extends through a wall of the riser of the catalytic cracking system. The spray nozzle assembly includes an elongated liquid deflection member supported by the pipe formed nozzle body within the mixing zone which defines an impingement surface against which pressurized liquid hydrocarbon directed through a liquid hydrocarbon inlet impinges and is transversely directed from the impingement surface into the mixing zone for atomization and direction through the barrel extension zone by a stream of pressurized steam.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a divisional of U.S. patent application Ser.No. 15/023,472, filed Mar. 21, 2016, which claims the benefit of U.S.Provisional Patent Application No. 61/880,320, filed Sep. 20, 2013, bothof which are incorporated by reference.

FIELD OF THE INVENTION

The present invention relates generally to liquid spray nozzles, andmore particularly, to spray nozzle assemblies particularly adapted foratomizing and spraying a liquid feed to a fluidized catalytic crackingriser reactor.

BACKGROUND OF THE INVENTION

A spray nozzle assembly of the foregoing type is shown and described inU.S. Pat. No. 5,921,472, the disclosure of which is incorporated byreference. Such spray nozzle assemblies typically include a nozzle bodywhich defines a mixing chamber into which a liquid hydrocarbon andpressurized gas, such as steam, are introduced and within which theliquid hydrocarbon is atomized. To enhance liquid atomization within themixing chamber, an impingement pin extends into the chamber and definesliquid impingement surface on the center line of the mixing chamber indiametrically opposed relation to the liquid inlet against which apressurized liquid stream impinges and is transversely dispersed andacross which pressurized steam from a gas inlet is directed for furtherinteraction and shearing of the liquid into fine droplets. The atomizedliquid within the mixing chamber is directed under the force of thepressurized steam through an elongated tubular barrel, commonly disposedwithin a wall of the catalytic reactor riser, for discharge from a spraytip at a downstream end thereof within the riser. Notwithstandingpassage through the elongated tubular barrel the liquid must dischargeas a very fine liquid particle spray for optimum performance. Toefficiently breakup and transmit the liquid hydrocarbon, the steam crossflow must be at a high volume and pressure, approximately 110 psi, andthe liquid pressure must be kept at approximately the same or greaterpressure.

In such spray nozzle assemblies, the liquid hydrocarbon flow stream mustpass through half the diameter of the mixing chamber before it impactsthe impingement pin. Particularly in spray nozzle assemblies withrelatively large diameter mixing chambers, such as those having a mixingchamber of four inches and more in diameter, there can be a tendency forthe liquid hydrocarbon flow stream introduced into the mixing chamber toonly partially impact the impingement surface of the impingement pin.The reason for this is that the liquid flow stream must pass asignificant distance through the mixing chamber where it is subjected toa heavy cross flow of steam before impacting the impingement surface.This tends to cause a shift in the liquid flow stream away from thecenter of the impingement surface, the magnitude of which is dependentupon the velocities of the pressurized steam and liquid flow streams fora particular setup. The shift prevents a portion of the liquidhydrocarbon flow stream from being shattered against the impingementpin, resulting in a significant increase in droplet size for a portionof the spray volume that adversely affects the spray performance. Inorder to overcome such shift in the liquid flow stream introduced intothe mixing chamber, heretofore it has been necessary to increase theliquid pressure even more to overcome the effect of the steam crossflow. This necessitates the need for larger and higher pressure processpumps that are more expensive to operate and more susceptible tobreakdowns. On the other hand, operation of such spray nozzles at lowerpressures significantly effects spray performance and can createclogging, particularly when spraying heavier crude oils such as residsand petroleum bottoms.

SUMMARY AND OBJECTS OF THE INVENTION

It is an object of the present invention to provide a liquid hydrocarbonspray nozzle assembly that is adapted for more effective and finerliquid atomization and improved spray performance in catalytic crackingreactors.

Another object is to provide a spray nozzle assembly as characterizedabove that can be efficiently operated at lower liquid pressures, nearlyhalf that of conventional catalytic cracking spray nozzle assemblies,with lesser expensive processing equipment.

A further object is to provide a spray nozzle assembly of the foregoingtype in which the liquid hydrocarbon flow stream introduced into themixing chamber of the spray nozzle body is not adversely effected by thepressurized steam prior to engaging an impingement surface that shattersand transversely directs the liquid within a mixing zone.

Still another object to provide a spray nozzle assembly of the abovekind that reduces the amount of steam necessary for effective liquidatomization.

Yet a further object is to provide a spray nozzle assembly of such typethat is effective for efficiently atomizing relatively heavy crude oils,such as resids and petroleum bottoms, without clogging or plugging ofthe spray nozzle components.

Another object is to provide such a spray nozzle assembly that has arelatively simple and durable design which lends itself to economicalmanufacture.

Other objects and advantages of the invention will become apparent uponreading the following detailed description and upon reference to thedrawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic depiction of a spray nozzle assembly in accordancewith the present invention mounted within the wall of a riser of acatalytic cracking reactor;

FIG. 2 is an enlarged longitudinal section of the spray nozzle assemblyshown in FIG. 1;

FIG. 3 is an enlarged transverse section taken in the plane of line 3-3in FIG. 2;

FIG. 4 is an enlarged perspective of an upstream end of the illustratedspray nozzle assembly; and

FIG. 5 is a side view of the liquid injector and associated steamorifice ring subassembly of the illustrated spray nozzle assembly.

While the invention is susceptible of various modifications andalternative constructions, a certain illustrative embodiment thereof hasbeen shown in the drawings and will be described below in detail. Itshould be understood, however, that there is no intention to limit theinvention to the specific form disclosed, but on the contrary, theintention is to cover all modifications, alternative constructions, andequivalents falling within the spirit and scope of the invention. Inthat regard, while the illustrated spray nozzle assembly is particularlyeffective for atomizing and spraying liquid hydrocarbons in catalyticcracking systems, it will be understood that the utility of the nozzleassembly is not limited to that usage.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now more particularly to the drawings there is shown andillustrative spray nozzle assembly 10 in accordance with the inventionmounted in a conventional manner in an insulated wall 11 (shown inphantom) of a riser of a fluidized catalytic reactor. The spray nozzleassembly 10 is supported in a tubular sleeve 12 fixed within the wall 11at an acute angle to the vertical for discharging atomized liquidhydrocarbon upwardly into the riser. The tubular sleeve 12 in this casehas an outwardly extending flange 14 to which a support flange 15 fixedto the spray nozzle assembly 10 may be secured.

The illustrated spray nozzle assembly 10, as best depicted in FIG. 2,basically comprises a nozzle body in the form of an elongated tubularmember 17 that defines a mixing zone 20 adjacent an upstream end havinga pressurized steam inlet 21 and a liquid hydrocarbon inlet 22 disposedon an outer side of the wall 11 of the riser and an elongated barrelextension zone 24 communicating with the mixing zone 20 disposed in andextending downstream through the nozzle support sleeve 12 and riser wall11. A spray tip 25 having one or more discharge orifices 26 is supportedat a downstream end of the tubular member 17 within the riser fordischarging and directing the atomized liquid spray. The tubular member17 may be one or more lengths of pipe, such as Schedule 80 steel pipe,having an internal diameter of between about 2 to 8 inches.

In accordance with the invention, the spray nozzle assembly is operablefor atomizing liquid hydrocarbon into a finer liquid particle dischargefor more efficient spray performance while operating at significantlylower liquid pressures. To this end, the liquid hydrocarbon inlet 22 isdisposed at an upstream end of the nozzle body tubular member 17 and thesteam inlet 21 communicates with through a side wall of the tubularmember 17. In the illustrated embodiment, the steam inlet 21 includes afitting 30 having a mounting clamp 31 for securement to a supply line 32coupled to a steam or other gas supply and a downstream end with acounter bore section 34 that fits within an opening 35 of the tubularmember 17, which in this case is formed with an inwardly tapered conicalside wall for facilitating securement of the fitting 30 to the tubularmember 17 by an appropriate annular weldment. The stem inlet fitting 30has a central flow passageway 36 with a steam inlet passage section 36 acommunicating through the tubular member 17.

The liquid inlet 22, like the steam inlet 21, includes a fitting 40having a mounting flange 41 for securement to a liquid hydrocarbonsupply line 42 coupled to a suitable liquid hydrocarbon supply and adownstream cylindrical section 44 for securement to an upstream axialend of the tubular member 17. The ends of the liquid inlet fitting 40and the tubular member 17 are chamfered for facilitating securement by aweldment. The liquid inlet fitting 22 includes an orifice member 45 fordefining a liquid inlet passage 46 of predetermined diameter throughwhich the feed liquid is accelerated. The orifice member 45 in thisinstance has a conical entry section for channeling the pressurizedliquid flow stream into and through the orifice member passage 46.

In carrying out this embodiment, the liquid inlet 22 includes anelongated closed end liquid injector 50 extending into the mixing zone20 along a central axis 51 thereof, which has a liquid extensionpassageway 52 communicating between the orifice member 45 and aplurality of discharge orifices 54 adjacent a downstream end of theextension passageway 52 which transversely direct liquid into the mixingzone 20 in perpendicular relation to the central axis 51. The liquidinjector 50 in this case is a separate tubular member having a closeddownstream end fixedly mounted with an upstream end in abutting relationto a downstream end of the liquid orifice member 45. The liquid injector50 has an upstream outwardly extending annular flange 55 that is clampedbetween a shoulder defined by an annular end 38 of the fitting 40 andthe downstream end of the orifice member 45, which is threadedly mountedwithin the fitting 40. It will be understood that alternatively theorifice member 45 and the liquid injector 50 could be made as a singlepart. In this instance, the central extension passageway 52 of theliquid injector 50 has an upstream passage section 52 a larger indiameter than the orifice member passageway 46 for allowing unimpededflow of liquid hydrocarbon into the injector 50, which then is channeledinto a smaller downstream passage section 52 b.

In further keeping with this embodiment, the liquid injector 50 has aclosed downstream terminal end 58 with an “x” configuration of theliquid discharge orifices 54. The discharge orifices 54 in this case aredefined by cylindrical passages that extend radially outwardly inperpendicular relation to the central axis 51 and define a flat internalimpingement surface 60 perpendicular to the central axis 51 againstwhich pressurized liquid hydrocarbon communicating through the extensionpassageway 52 impinges and is transversely directed and spread out intothe mixing zone 20.

In further carrying out this embodiment, an annular steam wall 64 andorifice ring 65 are disposed within the tubular member 17 adjacent adownstream end of the liquid injector 50, which supports the liquidinjector 50 and defines a plurality of concentrating steam dischargeorifices 66 at the specific locations of each injector discharge orifice54 for causing steam to directly interact with and atomize the liquidflow streams discharging from the liquid injector 50. The annular steamwall 64 in this case is a plate like wall member welded within thetubular body member 17 for defining an annular steam chamber 68 aboutthe liquid injector 50 upstream of the liquid discharge orifices 54 intowhich steam from the steam inlet 21 is directed. The orifice ring 65 inthis case is disposed within the annular steam wall 64 and has an axiallength of about twice the width of the wall 64 such that a portionextends a length upstream of the annular steam wall 64.

For defining the concentrating steam discharge orifices 66, a downstreamend section of the liquid injector 50 is formed with external flats 70across the liquid discharge orifices 54 and angled or rounded corners 71connecting the flats 70. The orifice ring 65 has a generally rectangularinternal opening with opposing sides formed with recesses 74 supportingthe corners 71 of the liquid injector 50 and with rounded corners 75adjacent the liquid injector flats 70 for defining the steam dischargeorifices 66 between the flats 70 and rounded corners 75 in alignedrelation to liquid discharge orifices 54. The steam discharge orifices66 defined by the steam orifice ring 65 and liquid injector flats 70 inthis case are aligned with and partially overlap each liquid injectordischarge orifice 54. Preferably, the downstream end of the steamorifice ring 65 is centered over or slightly upstream of the liquiddischarge orifices 54.

As can be seen, since the concentrating steam discharge orifices 66 arealigned precisely with the liquid discharge orifices 54 of the liquidinjector 50, they will direct steam over liquid discharge orifices 54for direct shearing and atomizing the liquid stream at the preciselocation where the liquid hydrocarbon exits the liquid injector 50.Since all of the energy of the steam is focused at that location, theliquid can be atomized into very fine liquid particles for transmissionto the spray tip 25. Since the concentrating steam orifices 66 arerelatively small, the steam inlet passage 36 a may be relatively large,such as one half the diameter or greater than the steam chamber, forachieving the desired velocity of steam through the orifices 66.

It has been found that the droplet size of the atomized liquid furthercan be varied by changing the area of the steam orifices 66. Foreffecting smaller atomized liquid droplets, the concentrating steamdischarge orifices 66 may be enlarged such as by changing the size ofthe injector flats 70 in relation to the internal opening of the orificering 65. In addition, auxiliary steam discharge orifices 66 a may beprovided about the outer perimeter of the steam orifice ring 65 byforming the outer perimeter of the ring 65 with flats 80, as depicted inFIG. 3. Preferably, the flats 80 are disposed radially outwardly of thecorners 71 of the liquid injector 50 so as to space the auxiliary steamdischarge orifices 66 a circumferentially between the inner steamdischarge orifices 66.

The steam orifice ring 65 preferably is welded to the corners 71 of theliquid injector 50 for maintaining proper orientation of the ring 65with respect to the injector 50. This further enables easy assembly ofthe liquid injector 50 and steam orifice ring 65 or a subassembly intothe tubular member 17 of the nozzle body and the central opening of thesteam chamber wall 64. The downstream end 58 of the liquid injector 50and the steam orifice ring 65 can be mounted in the central opening ofthe steam chamber wall 64 during assembly with a slip fit which willallow the injector 50 and orifice ring 65 assembly to thermally expandor contract without restriction. The end 58 of the liquid injector 50protruding through the steam orifice ring 65 and chamber wall 64 in thiscase is rounded for facilitating direction of the atomized liquiddownstream into the barrel zone 24 of the nozzle body.

In operation, it will be seen that steam directed into the steam inlet21 will enter the steam chamber 68 defined upstream of the steam chamberwall 64 and will be directed through the four circumferentially spacedconcentrating steam discharge orifices 66 at the precise location of theliquid injector discharge orifices 54 for enhanced interaction andatomization of liquid discharging from the liquid injector 50 followingimpingement upon the internal impingement surface 60 of the liquidinjector 50. The resulting increased atomization efficiency enables thespray nozzle assembly to be operated at liquid pressures as low as 60psi, or nearly half that the pressure requirements of conventionalcatalytic cracking spray nozzle assemblies. The focused direction ofsteam from the orifice ring 65 also reduces the quantity of steamnecessary for effective atomization. The more efficient pressurized airatomization of the liquid hydrocarbon further is effective for breakingup even heavier crude oils, such as resids and petroleum bottoms,without plugging or clogging of the nozzle components. Yet the spraynozzle assembly still has a very simple and durable design which lendsitself to economical manufacture and reliable usage.

1. A catalytic cracking system comprising: a riser; a spray nozzleassembly supported within a wall of the riser for discharging atomizedliquid into the riser; said spray nozzle assembly including an elongatedpipe formed nozzle body, said pipe formed nozzle body being made of oneor more lengths of cylindrical pipe, said pipe formed nozzle bodydefining a mixing zone and an elongated barrel extension zone longer inlength than the mixing zone downstream and in communication with themixing zone extending through the riser wall, a liquid hydrocarbonsupply, a liquid hydrocarbon inlet supported by said elongated pipeformed nozzle body through which a pressurized liquid hydrocarbon streamfrom said liquid hydrocarbon supply is directed into said mixing zone,an elongated liquid deflection member supported by said pipe formednozzle body within said mixing zone and defining an impingement surfaceagainst which pressurized liquid hydrocarbon directed into and throughsaid liquid hydrocarbon inlet impinges and is transversely directed fromsaid impingement surface in said mixing zone; a steam supply, a steaminlet supported by said elongated pipe formed nozzle body through whichpressurized steam from said steam supply is directed into said mixingzone for atomizing liquid hydrocarbon impinging upon and transverselydirected from said impingement surface and directing the atomized liquidhydrocarbon into and through said barrel extension zone; a spray tipsupported by said pipe formed nozzle body at a downstream end of saidbarrel extension zone having a discharge orifice through which atomizedliquid hydrocarbon directed into and through said barrel extension zoneis discharged in a predetermined spray pattern.
 2. The catalyticcracking system of claim 1 in which said elongated nozzle body is madeof more than one length of cylindrical pipe.
 3. The catalytic crackingsystem of claim 2 in which said impingement surface is disposedinternally within said elongated liquid deflection member.
 4. Thecatalytic cracking system of claim 3 in which said elongated liquiddeflection member has a central liquid passage communicating betweensaid liquid hydrocarbon inlet and said impingement surface, and saidelongated liquid deflection member includes a plurality of liquidhydrocarbon discharge orifices adjacent said impingement surface andtransverse to said central liquid passage for directing liquidhydrocarbon transversely relative to said central liquid passage intosaid mixing zone.
 5. The catalytic cracking system of claim 1 in whichsaid steam inlet communicates with said mixing zone through a side wallof said pipe formed nozzle body.
 6. The catalytic cracking system ofclaim 1 in which said liquid deflection member has a closed downstreamend which defines said internal impingement surface against which liquidhydrocarbon directed through said central liquid passage impinges. 7.The catalytic cracking system of claim 6 in which said impingementsurface is defined by said plurality of said liquid injector dischargeorifices.